Specimen Preparation

Reasons for Rejection

Fixed specimen

Frozen specimen

Delayed or improper handling

Comments

Submission of completed Prenatal Genetic Test Requisition Form is required. Submission of maternal blood specimen (4mL EDTA) is required, and submission of paternal blood specimen (4mL EDTA) is highly recommended since this test includes microarray analysis on amniotic fluid cells, maternal sample, and paternal sample, as well as maternal cell contamination study. To obtain a test requisition form, please call (614) 722-5321 and speak with a laboratory genetic counselor.?If the mother and the father of pregnancy are known to be consanguineous, please provide reported parental relationship information on the requisition form.

This microarray analysis can be performed on direct amniotic fluid specimen or on cultured amniocytes (cells grown from amniotic fluid). If test performed on cultured amniocytes, results are available in 10 days from when cultured cells become availavle for testing. Amniotic fluid chromosome analysis can be performed concurrently with, prior to, or as a reflex test to this prenatal microarray analysis.

This chromosomal (whole genome) microarray analysis uses a combination of oligonucleotide probes as well as SNP probes. Detection of DNA copy number abnormalities is performed by comparative genomic hybridization (CGH) analysis using ~135,000 oligonucleotide probes, while detecton of the regions of homozygosity (ROH, also known as long contiguous stretch of homozygosity) is done by single nucloeotide polymorphism (SNP) analysis using ~67,000 SNP probes.

Chromosomal microarray analysis evaluates DNA copy number across the genome at higher resolution than chromosome analysis. It can detect submicroscopic genomic losses and gains not detectable by chromosome analysis, as well as large genomic losses and gains that are detectable by chromosome analysis (such as trisomies, monosomies, triploidy, unbalanced translocations, and unbalanced inversions). Chromosomal microarrays that incorporate single nucleotide polymorphism (SNP) probes can detect large regions of homozygosity (ROH). Presence of ROH is not diagnostic of any disorder, but it can suggest increased risk for two different classes of genetic disorders: disorders of imprinting (uniparental disomy; UPD) and recessive disorders. Evidence suggestive of a blood relationship between the parents (parental consanguinity) also may be revealed.

PLEASE NOTE: Microarray analysis may not be able to detect the presence of mosaism if abnormality is present in less than 30% of cells. Microarray analysis also cannot detect balanced chromosomal rearrangements such as a balanced translocation or inversion.